The Bosnian Serbs want more autonomy
Crisis talks aiming to end years of political stalemate among leaders of Bosnia's divided communities have ended with no tangible results.
The talks were called by the EU and US in a bid to bring in constitutional reform and prepare Bosnia for eventual EU and Nato membership.
But representatives of the three main ethnic groups rejected the proposals.
The talks failure leaves post-war Bosnia more fragile than ever, reports the BBC's Mark Lowen in Belgrade.
Fourteen years after Bosnia's devastating war of independence came to an end, there are fears that a new conflict could erupt.
Balkan-watchers say they are disappointed, but not surprised, at the breakdown of these talks, our correspondent says.
The initiative had aimed to lay the groundwork for closure of the Office of the High Representative, the top international body in the country, in order to allow Bosnia to move towards Nato and EU membership as a self-governing, unified state.
The Bosniaks (Bosnian Muslims) and Croats said the proposed reforms did not sufficiently strengthen state institutions.
But for the Bosnian Serb Prime Minister Milorad Dodik the package went too far.
The Bosnian Serbs strongly oppose any moves that would jeopardise their desire for more autonomy, and Mr Dodik said the proposal risked diluting the power of his part of Bosnia, the Republika Srpska.
The country is struggling to stay together, our correspondent says, and Mr Dodik has repeatedly called for a referendum on the right of his entity to secede.
Swedish Foreign Minister Carl Bildt, who was the first international high representative in Bosnia after the war, led the push to break the impasse.
He was joined by US Deputy Secretary of State Jim Steinberg and Ollie Rehn, the EU's enlargement commissioner.
In a joint statement, Mr Bildt and Mr Steinberg insisted "limited progress" had been made, despite the apparent failure of the talks.
They called for some of the participants to show "greater determination and flexibility".
International diplomats are set to return to Bosnia in coming weeks to push for more negotiations.
The current high representative in Bosnia, Valentin Inzko, has described the situation in the country as serious.
"Bosnia is in a state of paralysis," he told the BBC ahead of the talks.
"Things are not moving at the moment. And I deeply regret all this nationalist rhetoric. It's not helpful, it's destructive and many, many wars have started with bad rhetoric. So we should really avoid it."
Under the 1995 Dayton peace accords which brought an end to the conflict, two separate entities were created in Bosnia - a Bosniak-Croat federation and a Serb republic.
They are linked by a common parliament, a three-member presidency and a council of ministers - but the division of authority remains unclear, and each side interprets it in different ways.